1. Field of the Invention
The invention relates to a process for the continuous preparation of hydroxyalkylamides from carboxylic esters and hydroxyalkylamines.
2. Discussion of the Background
DE-A 25 09 237 describes a process for preparing hydroxyalkylamides. In this process, esters and hydroxyalkylamines are reacted batchwise in the presence or absence of a solvent to give the end product. The reaction takes a number of hours.
The process is improved in EP-A-O 473 380. The temperature is selected so that a crystal slurry is formed during the reaction. The partial crystallization leads to yield improvements, since the undesirable formation of dimers of the target molecule, which is associated with elimination of hydroxyalkylamine, is suppressed. Here too, the reaction is carried out batchwise. The reaction time is a number of hours.
These synthetic methods practiced hitherto have various disadvantages: if the reaction is carried out in a solvent, the solvent has to be removed again afterwards.
The customary preparation requires slow dropwise addition of the hydroxyalkylamine.
The technique of working in a crystal slurry requires accurate correlation of viscosity and temperature, since excessive crystal formation reduces the yield. In addition, the discharge of the crystal slurry from the reactor and the subsequent compounding of the material are complicated.